1. Technical Field
The present invention relates to an apparatus and method for injecting fuel into internal combustion engines, particularly compression ignition engines
2. Background
Until the recent past, the known electronically controlled means of injecting fuel into modern diesel engines could be divided in two functionally different types: mechanically actuated systems and common rail systems. Both of these systems have their inherent advantages and disadvantages that dictate the choice of the system for a particular application. For instance, high pressure common rail systems rarely appear on today's heavy-duty diesel engines due to durability constraints related to the presence of very high fuel pressure in the rail and in the complex network of hydraulic lines for most of the engine operating time.
An integrated diesel fuel injection system has been proposed which combines the two separate types of systems as above into a single injection apparatus, allowing the engine management system to select the functional mode according to engine operating conditions. Such a system makes use of the mechanical actuation principle of the well-known unit injection systems to create high pressure for fuel injection, thereby avoiding durability limitations of the high pressure common rail systems, and can provide common rail-type injections in such conditions where lower injection pressure is beneficial and where extreme flexibility of injection timing is required. The common rail functional mode is secured in this known integrated fuel injection system through the use of a rail that is common for a set of injectors and that is fed with fuel under pressure by a separate pump. This arrangement works well but the total cost of the integrated fuel injection system would typically exceed that of an ordinary unit injection or common rail systems because of the presence of two fuel pressurization modules—unit injection plunger and the common rail pump.